The present invention relates to compressors. More particularly, the present invention relates to compressors that have shaft seals for preventing leakage of refrigerant from the internal space,of the compressor about the drive shaft.
In compressors that perform compression and intake by rotation of a drive shaft, a seal is typically provided for preventing leakage of refrigerant from the inner space about the drive shaft. Generally, this kind of seal is positioned to seal between the intake pressure area, which has a lower pressure than the discharge pressure area, and the atmosphere. Or, in a variable displacement compressor having an inclining swash plate, the seal device is positioned to seal between the operating chamber, which accommodates the swash plate, and the atmosphere.
However, as described in Japanese Unexamined Patent Publication No. 8-110104, the seal must withstand a great burden when carbon dioxide (CO2), the refrigerant pressure of which is ten times greater than that of fluorocarbon-based refrigerant, is used as refrigerant. The great burden shortens the life of the seal. In a variable displacement compressor that controls the inclination of the swash plate by varying the pressure of the operating chamber, the pressure of the operating chamber is higher than the intake pressure of a fixed displacement compressor, thus increasing the burden on the seal.
The objective of the present invention is to improve the reliability of the seal device of a compressor that uses a high-pressure refrigerant like CO2 by decreasing the burden on the seal device.
To achieve the above objective, the present invention provides a compressor having a shaft seal. The compressor includes a housing, an intake chamber located within the housing, a discharge chamber located within the housing, an operating chamber located within the housing, and a gas compressing mechanism located within the housing. At least a portion of the compressing mechanism is located within the operating chamber. The compressing mechanism draws refrigerant gas from the intake chamber and discharges the refrigerant gas to the discharge chamber. The compressor further includes a drive shaft extending between the interior of the housing and the exterior of the housing. The drive shaft drives the compressing mechanism. The compressor further includes a seal for preventing leakage of refrigerant gas from the interior of the housing to the atmosphere. The seal seals a gap between the drive shaft and the housing. One side of the seal is exposed to the atmosphere. The compressor further includes an isolation chamber formed in the housing to surround a portion of the drive shaft. One side of the seal is exposed to the interior of the isolation chamber. A pressure difference is applied to the seal by the difference between the pressures of the isolation chamber and the atmosphere. The compressor further includes a pressure reducing device for reducing the pressure in the isolation chamber when the compressor is operating. The pressure reducing device reduces the pressure difference applied to the seal and lowers the pressure in the isolating chamber with respect to that of the operating chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.